Organic light-emitting diodes (OLEDs) exploit the propensity of materials to emit light when they are excited by electrical current. OLEDs are of particular interest as an alternative to cathode ray tubes and liquid-crystal displays for production of flat visual display units. Owing to the very compact design and the intrinsically low power consumption, devices comprising OLEDs are suitable especially for mobile applications, for example for applications in cellphones, smartphones, digital cameras, mp3 players, laptops, etc. In addition, white OLEDs give great advantages over the illumination technologies known to date, especially a particularly high efficiency.
The prior art proposes numerous materials which emit light on excitation by electrical current.
P. Mathew et al., (J. Am. Chem. Soc., 2008, 130, 13534) reported the synthesis of 1,2,3-triazolylidenes, also known as abnormal carben or mesoionic carbine, and their use as versatile carbene ligands for late transition metals. Among others the synthesis of the following iridium carbene complex is described:
The abnormal triazolylidene complexes are expected to have a great potential for the development of new catalysts.
WO2011/139704A2 discloses the use of transition metal complexes comprising 1,2,3-triazolylidene carbenes, focusing mainly on monodentate ligands for catalytic applications.
K. F. Donnelly et al. (Organometallics, 2012, 31, 8414) reported the use of bidentate ligands bearing one 1,2,3-triazolylidene carbene moiety coordinating to platinum and iridium metal centers:
No application for this metal complexes is reported.
D. G. Brown et al. (J. Am. Chem. Soc. 2013, 135, 1692) reported the synthesis of 1,2,3-triazolylidene carbene-based pincer ligands for the synthesis of ruthenium complexes for light harvesting complexes for application in dye-sensitized solar cells.
Even though there are already known Ir and Pt carbene complexes which are suitable for use in OLEDs, especially as light-emitting substances, it is desirable to provide more stable and/or more efficient compounds which are usable in industry.